The purpose of this study is to examine the role of oxygen and oxy-radicals in phagocytic killing by polymorphonuclear leukocytes (PMNs). Non-myeloperoxidase mechanisms of oxidative killing will be emphasized, although the possibility of singlet oxygen production by hypochlorite (produced by myeloperoxidase) - hydrogen peroxide will be examined. The research plan involves both chemical and spectroscopic studies of the oxidative chemistry in the phagosome. A series of singlet oxygen and free radical scavengers will be characterized with respect to both their ability to scavenge singlet oxygen and their reactivity with different types of oxy-radicals (e.g. hydroxy, alkoxy, and alkylhydroperoxy radicals). Mixtures containing two of the scavengers will be introduced into the PMNs as a mixture in emulsified paraffin oil or adsorbed (or chemically bonded) to latex beads. After 1 h the scavengers and their products will be extracted and isolated. Analysis and quantitation will involve the use of high performance liquid chromatography and gas-liquid chromatography. Analysis of the results will be simplified if the involvement of singlet oxygen in these oxidations is verified. Linoleic acid, a molecule that is reported to give products with singlet oxygen that are not formed by free radical autoxidation, will be used as a specific chemical scavenger for singlet oxygen. Additional evidence for the participation of singlet oxygen will be obtained from studies using single photon counting techniques to measure PMN chemiluminescence dispersed by a monochrometer. Spectra from this instrumentation will have the resolution necessary to assign bands associated with singlet oxygen luminescence. The total chemiluminescence spectrum of the PMN will be recorded. The chemiluminescing species will be assigned based on the position of the emission maximum, fine structure of the luminescence bands (if any), and the effect of various excited state quenchers on the luminescence.